Posting Freak
Posts: 3,119
Threads: 271
Joined: 2008-11
For the first one:
Divide both sides by 6
2 = sqrt(2x-1) - sqrt(x-4)
subtract sqrt(2x-1) from both sides
2 - sqrt(2x-1) = - sqrt(x-4)
change the signs to make it easier
sqrt(2x-1) - 2 = sqrt(x-4)
square both sides
2x - 1 - 4sqrt(2x-1) + 4 = x - 4
rearrange
2x+7-x = 4sqrt(2x-1)
square again
x^2 + 14x + 49 = 32x - 16
rearrange
x^2 - 18x + 65 = 0
quadratic formula GO
x = 5, 13 and the sum is 18
Posting Freak
Posts: 3,119
Threads: 271
Joined: 2008-11
Second one is along the same lines.
divide by 2 gets you
1 = sqrt(x-3) - sqrt(2x-4)
rearrange
1 - sqrt(x-3) = -sqrt(2x-4)
change sign
sqrt(x-3) - 1 = sqrt(2x-4)
square both sides
x - 3 - 2sqrt(x-3) + 1 = 2x - 4
rearrange
x - 2sqrt(x-2) - 2 = 2x - 4
then rearrange again
-x + 2 = 2sqrt(x-2)
square
x^2 - 4x + 4 = 4x - 8
rearrange
x^2 = -12
try to solve it and you're sqrting a negative, then you blow up the world. There is no solution.
Posting Freak
Posts: 1,691
Threads: 72
Joined: 2008-07
the second one is easy, they give you a limited number of x's to try. trying 3 choices is probably faster than factoring. first one is a better format to make you think. (yeah, i would actually do that on a test. use what your given.)